Electrocoating compositions are well known and disclosed in Gilchrist patents, U.S. Pat. No. 3,351,675; U.S. Pat. No. 3,362,899; U.S. Pat. No. 3,575,909; and U.S. Pat. No. 3,351,575 and the same are incorporated herein by reference. Electrocoating compositions are dispersed in dilute water baths and then electrocoated onto cathodic or anodic substrates submerged in the electrocoating bath. The electrocoated films can be heat cured with catalysts or cured by ultraviolet energy as disclosed in U.S. Pat. No. 4,040,925.
It now has been found that particularly useful anodic electrocoating compositions based on a fatty acid and unsaturated acid modified styrene-allyl alcohol polymers, further modified with acid functional acrylic copolymers, provide excellent electrocoating compositions for anode substrates. The electrocoating compositions exhibit high hydrophobic properties which impart excellent plating properties such as shut down, throwing power, as well as excellent cured film properties such as good water resistance and salt spray resistance. The electrocoating composition polymer is substantially free of readily hydrolysable ester groups in addition to contributing considerably to good electrical resistance properties and bath stability. The electrocoating compositions are particularly well suited to air-drying or force-drying wherein good post flow is obtainable. The electrocoated film quickly dries to handle or stack if desired. Baking at higher temperatures may also be used to cure the coating in which case an aminoplast curing agent may be advantageously employed. These and other advantages are achieved by the electrocoating composition of this invention.